Apple Newton Utilities Guide de l'utilisateur télécharger pdf (Page 416)

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101

CHAPTER 10

Recognition: Advanced Topics

10-40 Using Advanced Topics in Recognition

Customized Processing of Input Strokes 10

Setting the vStrokesAllowed flag provides the view with a means of intercepting

raw input data for application-speciﬁc processing. If this ﬂag is set, strokes are

passed one at a time as the argument to the view’s

ViewStrokeScript method.

Your

ViewStrokeScript method can then process the strokes in any manner

that is appropriate. The view’s

ViewStrokeScript method is invoked when the

user lifts the pen from the screen at the end of each input stroke.

Both the

vGesturesAllowed and vStrokesAllowed ﬂags invoke methods

that can be used to provide application-speciﬁc handling of gestures. However, the

vGesturesAllowed flag supplies system-defined behavior for the gestures tap,

double-tap, highlight, and scrub in

clEditView and clParagraphView views,

while the

vStrokesAllowed ﬂag does not provide any behavior that you don’t

implement yourself, regardless of the kind of view performing recognition.

For example,

clEditView and clParagraphView views handle system-

deﬁned gestures automatically. Thus, scrubbing in a

clParagraphView view that

sets the

vGesturesAllowed ﬂag does not invoke the ViewGestureScript

method because the view handles this gesture automatically. On the other hand, a

clView view would need to supply a ViewGestureScript method to process

the scrub gesture because this kind of view does not provide any gesture-handling

behavior of its own. Finally, remember that any view setting the

vStrokesAllowed

flag must also supply a

ViewStrokeScript method.

Setting these ﬂags causes the recognition system to send messages such as

ViewClickScript or ViewStrokeScript, passing a unit (an object that

describes the interaction of the pen with the tablet) as the argument to the

corresponding methods. Units are only valid when accessed from within the

methods invoked during the recognition process—you cannot save them for later

use. However, you can distribute the processing of unit data as appropriate; for

example, you might call the

GetPointsArray function from within your

ViewClickScript method and use the result later in your ViewIdleScript

method.

IMPORTANT

Do not save units for later use—they are valid only during the

recognition process. After the user interaction is complete and the

various scripts utilizing a particular unit have returned, the

memory allocated for that unit is freed explicitly. Subsequent use

of the unit may produce bus errors or loss of signiﬁcant data.

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Apple Newton Utilities Guide de l'utilisateur Page 416

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